The broad objectives of this research program are to develop new anticonvulsant drugs and to provide new information which may be useful in the elucidation of the mechanism of action of clinically useful agents. The compounds proposed for synthesis and examination have been designed on the basis of the suspected involvement of gamma-aminobutyric acid (GABA) in the etiology of at least some forms of epilepsy and in the mechanism of action of several useful antiepileptic agents. A working hypothesis is developed suggesting that the cyclic imide moiety of hydantoins, succimimides, and related drugs and the pseudo imide moiety of benzodiazepines may be functioning as a bioisosteric compliment of the carboxyl group of GABA. This hypothesis allows the prediction that the introduction of a suitably positioned basic moiety will lead to enhanced activity and/or selectivity of action. Potential synthetic routes to compounds possessing these features in hydantoin and pyrrolidinedione prepared for anticonvulsant activity will then allow a tentative evaluation of the hypothesis which can be further examined by more specific pharmacological experiments and the preparation of additional analogs.